Digital read-out watches of the type with which the present invention is concerned are shown and described in my copending U.S. patent applications, Ser. No. 516,688 filed Oct. 21, 1974 entitled ACTUATING MECHANISM FOR WRIST INSTRUMENTS; Ser. No. 538,743 filed Jan. 6, 1975 entitled ACCELERATION/DECELERATION ACTUATING MECHANISM FOR WRIST INSTRUMENTS; and Ser. No. 556,335 filed Mar. 7, 1975 entitled WRIST ACTUATED PRESSURE SWITCH. Essentially, a quartz crystal is used as an oscillator and the output frequency which is extremely stable is divided down into suitable clock pulses for actuating a digital display visible through a lens on the face of the watch. This display can be provided by light emitting diodes or liquid crystal displays and ordinarily requires some type of display illuminating means which may be actuated by a manually operable push-button on the side of the watch casing or by an inertia-responsive switch, such as shown in all of the foregoing pending patent applications.
The prior art quartz-type digital read-out watches all have a casing made of metal, provided with a top opening for accommodating a transparent lens for viewing the digital read-out. Further frame structures within the metal casing position the watch module which normally incorporates an integrated circuit chip and other components associated with the operation of the watch. In addition, there is provided a base plate or cap which threads into the main metal casing the same being removable for replacing batteries.
Major problems associated with the foregoing types of casings include the relatively high expense in the manufacture of the same. This expense is primarily a result of the use of metal and the necessary machining operations thereon. Further, insulation portions must be provided to prevent the metal casing from short-circuiting the terminals of various components within the casing. In this respect, since the metal casing is electrically conductive, it is vulnerable to static charge build-up and possible damage to the interior components. Further problems include the fact that metal is heavy thus increasing the overall weight of the watch. Also the metal casing construction at the portion it connects to the watchband normally requires special tools to install and remove the band.
Finally, when the batteries are received in the unthreadable base member the overall thickness of the watch is increased over that which would occur if the batteries could be disposed in another location. However, attempting to dispose the batteries in another location requires more metal for the casing and added insulation requirements.